The present invention relates to a method for repairing a protective lining of an industrial reaction or transport vessel, such as a converter vessel, electric arc furnace, or ladle, e.g. steel casting ladle, pig iron ladle, torpedo ladle or slag ladle. In particular, the present invention relates to a method for repairing a protective lining of an industrial reaction or transport vessel, wherein areas of the lining having a thickness below a pre-determined threshold value are identified and monolithic lining material is applied onto those areas.
Industrial reaction or transport vessels, such as blast furnaces, electric arc furnaces, ladles or converters, are e.g. used for metallurgical purposes such as for producing steel. These vessels generally have a protective lining at their inner surface, which protects the outer metallic surface of the vessel from being damaged by the heat or reaction conditions inside the vessel. However, the protective lining is subjected to wear during the use of the vessels and must be repaired from time to time to ensure high operational safety.
For this purpose, the residual thickness of the protective lining is measured between the individual phases of use of the vessel, when the vessel is empty. The residual thickness data obtained by this measurement are used to determine the areas of the lining which have to be repaired.
International Patent Application WO 01/38900 A1 discloses a non-contacting measuring procedure for measuring the residual thickness of the refractory lining of a metallurgical vessel. The method comprises sweeping a laser beam from a measuring device over the inner surface of the metallurgical vessel, i.e. the surface of the refractory lining, and measuring the angle and the distance between measuring device and inner surface of the vessel at various points. The measuring device preferably includes a laser diode operating in a pulse mode as a transmitting device and a photodiode as a receiving device. The thus obtained data allow to image the surface structure of the refractory lining in the form of a three-dimensional thickness profile. WO 01/38900 A1 suggests that the measuring device is physically associated with a device which applies new lining material to the inside surface of the vessel.
However, the lining material is generally applied manually to the inside surface of the vessel, either by means of an operator holding a repair device or by means of a repair device which is manually manipulated by an operator via a remote. In both cases the operator must be able to visibly identify the areas to be repaired and follow the movements of the repair device. Therefore, the operator has to be relatively close to the open-end of the vessel to be repaired. This is connected with several drawbacks. The operator is exposed to heat, fire, rebound of new lining material and other parts falling off the vessel. Furthermore, there is the danger of explosion in the vessels, if the hot material gets into contact with water, which may cause harm to the operator, if the operator is close to the vessel.
Moreover, the manual method is inherently connected with human errors. For instance, if the operator misses the right spot to be repaired, e.g. by a few centimeters, there is the danger of causing a so called “breakthrough”, which is a hole in the wall of the vessel, and may harm the operator of the vessel or damage the equipment connected with the vessel or even lead to explosions if the material flowing out of the vessel comes in contact with water. This may be a problem because it is difficult to visibly identify the areas to be repaired if the protective lining is entirely monolithic, and the operator can only obtain a rough guidance by the measurement of the thickness profile carried out before.
If the operator actually holds the repair device, the output of new lining material is generally limited. Furthermore, because of the heat, repair time under control of an operator is generally limited to 10 to 15 minutes.
Accordingly it would be highly desirable to provide a method for repairing a refractory lining of a metallurgical vessel which is more accurate than the methods according to the state of the art, using less material and which eliminates the operational dangers mentioned before.